The International Organization for Standardization/International Electrotechnical Commission (ISO/IEC) Moving Picture Experts Group-4 (MPEG-4) Part 10 Advanced Video Coding (AVC) standard/International Telecommunication Union, Telecommunication Sector (ITU-T) H.264 standard (hereinafter the “MPEG4/H.264 standard” or simply the “H.264 standard”) is the first international video coding standard to include a Weighted Prediction (WP) tool. The scalable video coding (SVC) standard, which is currently being developed as an amendment of the H.264 standard (and is thus also interchangeably referred to herein as the “H.264 standard”), also adopts weighted prediction. However, the SVC standard does not specify how to handle the weights in motion compensated temporal filtering (MCTF) update step if weighted prediction is used in the prediction step.
Weighted Prediction is supported in the Main, Extended, and High profiles of the H.264 standard. The use of WP is indicated in the sequence parameter set for P and SP slices using the weighted_pred_flag field, and for B slices using the weighting_bipred_idc field. There are two WP modes, an explicit mode and an implicit mode. The explicit mode is supported in P, SP, and B slices. The implicit mode is supported in only B slices.
A single weighting factor and offset are associated with each reference index for each color component in each slice. In explicit mode, these WP parameters may be coded in the slice header. In implicit mode, these WP parameters are derived based only on the relative distance of the current picture and its reference pictures.
For each macroblock or macroblock partition, the weighting parameters applied are based on a reference picture index (or indices in the case of bi-prediction) of the current macroblock or macroblock partition. The reference picture indices are either coded in the bitstream or may be derived, e.g., for skipped or direct mode macroblocks. The use of the reference picture index to signal which weighting parameters to apply is bitrate efficient, as compared to requiring a weighting parameter index in the bitstream, since the reference picture index is already available based on the other required bitstream fields.
Many different methods of scalability have been widely studied and standardized, including SNR scalability, spatial scalability, temporal scalability, and fine grain scalability, in scalability profiles of the MPEG-2 and H.264 standards, or are currently being developed as an amendment of the H.264 standard.